Chapter 3 - Biological molecules - DNA replication and the genetic code

Question 1

what must happen to enable DNA to replicate

Answer 1

the double helix must unwind and the hydrogen bods holding the strands together must be broken

Question 2

what happens once the DNA strands have separated

Answer 2

free DNA nucleotides will pair with the comlementary bases (hydrogen bonds) then phosphodiester bonds form between the adjacent nucleotides

Question 3

explain the concept of semi-conservative replication

Answer 3

the new strands are made of one old strand and one new strand

Question 4

what are the enzymes involved

Answer 4

DNA helicase - unwinds the double strand (breaks hydrogen bonds)
DNA polymerase - forms phosphodiester bonds between the new nucleotides

Question 5

what is a mutation

Answer 5

when errors occur in the replication process

Question 6

what is meant by the triplet code and a codon

Answer 6

a codon codes for an amino acid and a codon is made of three basses

Question 7

what is a gene

Answer 7

a section of DNA that contains all the codons to code for a protein

Question 8

what is meant by the universal code

Answer 8

all organisms use the same code

Question 9

what is a start or stop codon and what purpose does this serve

Answer 9

the codons will be read in frame meaning that the gene always starts with the start codon and finishes with one of the three stop codons (which don’t code for an amino acid) the code is non-overlapping

Question 10

what is meant by degenerate

Answer 10

there are 64 possible codons and only 20 amino acids so the same amino acid can be coded for by more than one combination of bases